Abstract: "Background: The possible therapeutic impact of dietary changes on existing mental illness is largely unknown. Using a randomized controlled trial design, we aimed to investigate the efficacy of a dietary improvement program for the treatment of major depressive episodes.
Methods: ‘SMILES’ was a 12-week, parallel-group, single blind, randomised controlled trial of an adjunctive dietary
intervention in the treatment of moderate to severe depression. The intervention consisted of seven individual
nutritional consulting sessions delivered by a clinical dietician. The control condition comprised a social support
protocol to the same visit schedule and length. Depression symptomatology was the primary endpoint, assessed
using the Montgomery–Åsberg Depression Rating Scale (MADRS) at 12 weeks. Secondary outcomes included
remission and change of symptoms, mood and anxiety. Analyses utilised a likelihood-based mixed-effects model
repeated measures (MMRM) approach. The robustness of estimates was investigated through sensitivity analyses.
Results: We assessed 166 individuals for eligibility, of whom 67 were enrolled (diet intervention, n = 33; control,
n = 34). Of these, 55 were utilising some form of therapy: 21 were using psychotherapy and pharmacotherapy
combined; 9 were using exclusively psychotherapy; and 25 were using only pharmacotherapy. There were 31 in
the diet support group and 25 in the social support control group who had complete data at 12 weeks. The dietary
support group demonstrated significantly greater improvement between baseline and 12 weeks on the MADRS
than the social support control group, t(60.7) = 4.38, p < 0.001, Cohen’s d = –1.16. Remission, defined as a MADRS
score <10, was achieved for 32.3% (n = 10) and 8.0% (n = 2) of the intervention and control groups, respectively
(χ2 (1) = 4.84, p = 0.028); number needed to treat (NNT) based on remission scores was 4.1 (95% CI of NNT 2.3–27.8). A sensitivity analysis, testing departures from the missing at random (MAR) assumption for dropouts, indicated that the impact of the intervention was robust to violations of MAR assumptions.
Conclusions: These results indicate that dietary improvement may provide an efficacious and accessible treatment
strategy for the management of this highly prevalent mental disorder, the benefits of which could extend to the
management of common co-morbidities."